Currently available gravity roller conveyors typically use a pair of structural members to support each row of load-bearing rollers. Such a structure necessitates tedious fabrication techniques to assure uniform spacing between all of the structural members throughout the length of the conveyor. It is often desirable in such systems to stagger the placement of successive rollers to reduce the gap over which a load is unsupported. Typically, the staggering is achieved merely by adding one or more additional rows of rollers with their centers longitudinally offset from one another. Recent conveyor designs have incorporated rollers mounted on alternate sides between pairs of support structures; however, the need to accommodate the axles of successive rollers has restricted the ability of such designs to minimize the gap between successive rollers. To date, the only conveyor systems providing minimal gap between successive rollers require an excessive number of structural supporting members. Such designs exacerbate the fabrication difficulties of maintaining proper spacing between the structural supporting members.
To avoid the use of ballbearing type journals between the axles of conveyor rollers and the structural supporting members, some designs have used specially machined configurations of axles for retentively engaging apertures in the structural support members with various types of flanges, bushings and retainers. Other designs have used sleeve-type ball bearing assemblies interposed between the axles of the rollers and specially formed receptacles in the supporting structural members. Unique axles and specially formed receptacles both incur additional tooling and fabrication costs. Moreover, the often intricate interrelation between the specially formed receptacles and the unique axles or bearings tends to hinder the repair or replacement of damaged rollers, thereby unnecessarily contributing toward the maintenance cost of such conveyor systems.